Timing Issues With Large Buffer sizes

hi, i recently noticed that the large the buffer size is, more timing problems start to appear.
on 1024 - cubase miss about 50ms of the starting midi note.
on 2048 - the all project loss is timeing, delays gets out of sync.
my audio interface is RME Babyface Pro.
there is anybody who suffer from the same problem?
there is any bugs with cubase 8 delay compensation?
tnx a lot.

any help?